package demo;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * @Auther: hjy(lc))
 * @Date: 2022/7/21-07-21-11:07
 * @Description：demo
 */
public class Map_use {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<String,String>();
        map.put("1","value1");
        map.put("2","value2");
        map.put("3","value3");

        //第一张遍历方法，普遍使用，二次取值
        System.out.println("通过Map.keySet遍历key和value：");
        for (String key : map.keySet()) {
            System.out.println("key = " + key + " and value = " + map.get(key));
        }

        //第二种
        System.out.println("通过Map.entrySet使用iterator遍历key和value：");
        Iterator<Map.Entry<String,String>> it = map.entrySet().iterator();
        while (it.hasNext()){
            Map.Entry<String, String> entry = it.next();
            System.out.println("key = " + entry.getKey() + "and value= " + entry.getValue());
        }

        //第三种：推荐使用，尤其是容量大时
        System.out.println("通过Map.entrySet遍历key和value：");
        for (Map.Entry<String, String> entry : map.entrySet()) {
            System.out.println("key = " + entry.getKey() + "and value= " + entry.getValue());
        }

        //第四种
        System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
        for (String value : map.values()) {
            System.out.println("value = " + value);
        }
    }
}
